Heliosphere

Plasmas and their embedded magnetic fields affect the formation, evolution and destiny of planets and planetary systems. The heliosphere shields the solar system from galactic cosmic radiation. Our habitable planet is shielded by its magnetic fi eld, protecting it from solar and cosmic particle radiation and from erosion of the atmosphere by the solar wind. Planets without a shielding magnetic field, such as Mars and Venus, are exposed to those processes and evolve differently. And on Earth, the magnetic field changes strength and configuration during its occasional polarity reversals, altering the shielding of the planet from external radiation sources.

How important is a magnetosphere to the development and survivability of life? The solar wind, where it meets the local interstellar medium (LISM), forms boundaries that protect the planets from the galactic environment. The interstellar interaction depends on the raw pressure of the solar wind and the properties of the local interstellar medium (density, pressure, magnetic field, and bulk flow). These properties, particularly those of the LISM, change over the course of time, and change dramatically on long time scales (1,000 years and longer) as the solar system encounters interstellar clouds.

How do these long-term changes affect the sustainability of life in our solar system? Understanding the nature of these variations and their consequences requires a series of investigations targeting the structure of the heliosphere and its boundaries and conditions in the LISM. Planetary systems form in disks of gas and dust around young stars. Stellar ultraviolet emission, winds, and energetic particles alter this process, both in the internal structure of the disk and its interaction with its parent star. The role of magnetic fields in the formation process has not been fully integrated with other parts of the process.

The study of similar regions in our solar system, such as dusty plasmas surrounding Saturn and Jupiter, will help explain the role of plasma processes in determining the types of planets that can form, and how they later evolve.

On May 24, 2005 NASA's

Voyager 1 spacecraft had traveled far enough outward through our Solar System that it reached the heliosheath. This is an area just past the termination shock region, where the solar wind crashes into the thin interstellar gas of the galaxy.